Currently in a Long-Term Evolution-Advanced (LTE-A) system, at most 4 User Equipments (UEs) can be supported for joint scheduling. For MU-MIMO transmission, at most 4-layer transmission can be supported, and at most two data flows can be allocated to each UE. For joint scheduling, each UE is configured with its dedicated DeModulation Reference Signal (DMRS). Accordingly, 8 DMRS ports are reserved in the LTE-A system, with a corresponding number from R7 to R14, so that for SU-MIMO transmission, at most 8 layers transmission can be supported, i.e., each user can be configured with 8 data flows at most. The DMRS port is a virtual port, corresponding to a group of DMRSs. This group of DMRSs is used to demodulate data transmitted through the virtual port. In practical application, a same group of Resource Elements (REs) are multiplexed for 4 DMRS ports. For example, R7, R8, R11 and R13 are configured to use one group of REs, R9, R10, R12 and R14 are configured to use another group of REs. 4 DMRS ports using a same group of REs are distinguished via a 4-bit Orthogonal Cover Code (OCC). Resources allocated by a base station to multiple UEs by joint scheduling may be sent to these UEs through a downlink control signal, e.g. a Downlink Control Information (DCI) signaling. Table 1 shows values and corresponding information of an antenna port indicator in the DCI, where SCID stands for a scrambling identity of DMRS. As shown in Table 1, in the case of one codeword and the value of the antenna port indicator being 0-3, 4 UEs may be jointly scheduled with one layer for each UE; in the case of two codewords and the value of the antenna port indicator being 0-1, 2 UEs may be jointly scheduled with two layers for each UE.
TABLE 1Values and information of an antenna port indicator in DCIOne codewordTwo codewordsValueinformationValueinformation0One layer, port 7, SCID = 00Two layers, ports 7-8,SCID = 01One layer, port 7, SCID = 11Two layers, ports 7-8,SCID = 12One layer, port 8, SCID = 02Three layers, ports 7-93One layer, port 8, SCID = 13Four layers, ports 7-104Two layers, ports 7-84Five layers, ports 7-115Three layers, ports 7-95Six layers, ports 7-126Four layers, ports 7-106Seven layers, ports 7-137Reserved7Eight layers, ports 7-14